The present invention relates generally to telecommunication systems, and more particularly, to a system and method for updating an R-P connection when a mobile station roams from one radio network to another.
In a telecommunication system, as shown in FIG. 1, a packet data serving node (PDSN) 10a or 10b usually serves multiple radio networks (RNs), e.g., 12a, 12b and 12c. On the other hand, a single RN, e.g. 12b, can be in communication with more than one PDSN. When a mobile station (MS) roams from one RN to another, a RN-to-PDSN connection (R-P connection) 14 must be updated to maintain a smooth communication channel between the RN 12 and the PDSN 10.
FIG. 2 shows a communication infrastructure describing the relationship among a PDSN 10, base station controllers (BSCs) 16, 18, and 20, Visitor""s Location Registers (VLRs) or Mobile Service Centers (MSCs) 22, representative cells of radio networks 24a and 24b, and a roaming MS 26. For instance, when the MS 26 roams from one cell 28, which is under the control of the BSC 16, to another cell 30 controlled by the BSC 18, an old R-P connection 32 between the BSC 16 and the PDSN 10 may have to be updated to reflect a new R-P connection 34 between the BSC 18 and the PDSN 10. Furthermore, the MSC/VLR 22 may be in communication with both the BSC 16 and the BSC 18 without maintaining a communication channel with the PDSN 10.
In one scenario, when the MS 26 roams to a new radio network, and if a BSC serving the new radio network is under a different PDSN 10, the MS 26 may have to perform a mobile IP (M-IP) registration process. However, a race condition may happen during the M-IP registration when packets are still routed to the old network before the new M-IP registration has been completed. Hence, it is recommended by the Telecommunication Industry Association (TIA) to relay all these packets from the old radio network to the new radio network.
Although the TIA has dealt with the race condition during the M-IP registration, two other scenarios for switching the R-P connection are not contemplated by the TIA. In one scenario, the new BSC is under the same PDSN 10, but relates to a different MSC/VLR 22. As shown in FIG. 2, this could happen when the MS 26 roams into the territory of the BSC 20 from that of the BSC 16. In another scenario, the new BSC 20 is under the same PDSN 10 and relates to the same MSC/VLR 22. This occurs when the MS 26 moves from the control of the BSC 16 to the BSC 18.
Therefore, an improved method is needed for timely switching or updating an R-P connection when a MS 26 roams into a new radio network.
A system and method is provided for timely maintaining or establishing an R-P connection after a mobile station (MS) roams from the control of an old base station controller (BSC) to that of a new BSC.
In one embodiment of the present invention, a Mobile Service Center (MSC) or Visitor""s Location Register (VLR) stores packet data call status information including point to point protocol (PPP) session status information and configuration information about BSCs. The information may include related cells and pocket data service nodes (PDSNs) before the MS moves to a new radio network (RN). During a registration process of the MS 26, once a Location Update Request is received from the MS 26, the MSC/VLR 22 can check whether the MS 26 is in a PPP session and whether the MS 26 is moving to a new BSC but within the same packet zone. If so, the R-P connection can be switched over. In this case, the MSC/VLR 22 will inform the new BSC to establish the R-P connection with the PDSN 10.
In another embodiment of the present invention, an R-P connection is maintained between the old BSC and the PDSN 10 during a registration process while a routing connection is made between the old BSC and the new BSC.
In another embodiment of the present invention, the MS 26, instead of the MSC/VLR 22, stores necessary information such as a PPP session indicator and a cell ID. During the registration process, the new BSC receives information about the R-P connection between the old BSC and the associated PDSN 10 from the MS 26. Upon determining that a new R-P connection is needed, the PDSN 10 establishes the new R-P connection with the new BSC.
In another embodiment of the present invention, during an origination process, the MS 26 communicates directly with the new BSC. The new BSC subsequently communicates with the MSC/VLR 22 to obtain information about the old R-P connection. The new BSC establishes a new traffic channel with the MS 26 only if needed. The new BSC also checks the PPP session status information and triggers the construction of a new R-P connection.
In yet another embodiment of the present invention, if certain conditions require (e.g., the MS 26 is at an Inter-MSC 22 boundary cell), switching the R-P connection can be avoided. The packet traffic can be routed back to the old BSC via a base station to base station (BSxe2x80x94BS) link. Therefore there is no need to switch the R-P connection.
In another embodiment of the present invention, an R-P connection is initiated during a mobile termination process. Information about the old BSC and its link with the PDSN 10 is transferred to the new BSC.
In another embodiment of the present invention, an R-P connection is maintained during a mobile termination process by routing the packet traffic to the old BSC. A paging process is used for setting up a traffic channel between the new BSC and the MS 26.
In yet another embodiment of the present invention, information about the old R-P connection and the associated PDSN 10 are given to the new BSC through a hard handoff process. A new R-P connection is then established.